Evaporating apparatus



W. L. DE BAUFRE.

EVAPORATING APPARATUS.

APPLICMION HLED MAR13,1917.

'Patented sept. 13,1921.

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Specification ot Letten Patent. Patelited Sept. 13, 1921.

Application led Hatch 13, 1917. Serial No. 154,584.

To all whom it may concern Be it known that I, WILLIAM L. DE BAUFRE, acitizen of the United States, residing at Anna olis, in the lcounty ofAnne Arundel and tate of Maryland, have invented a new and usefulEvaporating Apparatus, of which the following is a specilcation.

My invention relates to apparatusv for evaporating and concentratingsolutions and for recoverin the products of distillation bycondensation, and has for its object the arranging and proportoning theseveral parts of such ap aratus so asto secure the most economicaf) andefficient operation, especially in those systems employing vapor comressors for regenerative working.

ith the foregoing and other objects in view, my invention consists ofthe novel construction, combination'and arrangement of parts ashereinafter specifically described and illustrated in the drawingswherein is shown4 the preferred embodiment of my invention, but it isunderstood that changes, variations and modifications can be resorted towhich come within the scope of the claims hereunto appended.

In the drawings of the herein described embodiment of my invention,Figure 1 shows a sectional view in elevation of my improved evaporatingapparatus' Fig. 2 is a sectional View taken through Al of Fig. 1..

In the evaporating apparatus as shown in the two figures, the evaporatorshells l and 3 constitute evaporating chambers, and within them arelocated the condensing chambers 2 and 4 respectively. The latter areillustrated as composed of helical coils of tubing connected to headersat top and bottom. The condenser shell 5 contains a similar condensingchamber 6, the reheater shell 7 a similar condensing cham er 8, and theheat exchanger shell 9 a similar cooling chamber 10.- Eleven and 12 areva or compressors of the ty e shown more in detail in i 3, 4 and 5.I'lhe numbers 15, 16, 17, 18 and 19 refer to devices for removingliquids from the several evaporatin and condensing chambers as will beexp ained later.

The plant is represented as having two effects onl shellV 1 with coils 2bein Vthe first effect, andy shell 3 with coils 4 ing the second effect.While this number of Y effects is sufficient to illustrate the operationof the apparatus, any number of additional effects may be added betweenthe second effect (shell 3) and the condenser (shell 5)'.

The primar va or is suf lied b main 20 through valvespQl' `and 52pm theysteam nozzles 12 and 14 of vapor compressors 11 and 13 respectively,through valve 23 directly to the condensing chamber 2 of the firsteffect, through valve 2 4 directly to the condensing chamber 4 of thesecond effect, and to such additional effects, pumps, etc., as ma berequired. Valves 25 and 26 control t e lsupply of secondary vapor fromthe evaporating chambers to the vapor compressors 11 and 13. and valves27 and 28 control the discharge therefrom of the commingled primary andsecondar vapors to the coils 2. A b -pass not s own could readily beprovided to convey these cammingled va ors to the coils 4 of the secondeffect. alves 29 and 30 control the dischar e of vapor from shells 1and- 3 respective y. Valve 3l controls the flow of vapor from the shell1 of the first effect into the coils 4 of the second effect. Valve 32'is a vapor by-pass from the first to the effects following the secondand to the condenser. Through valve 33, vapor is supplied the coils 8 ofthe preheater.

From pipe 34 the liquid resulting from the condensation of vapor withincoils 8, is drained away either b a valve manually operated orautomatica ly by a trap such as indicated by 1%'18 and 19 fordischarging the liquid forme in the condensing chambers 2, 4 and 6,respectively. Upon these indicate by the liquld level the roper workingof the float or bucket wit in the trap. At the tops of these traps areconnected :the air cocks 35, 36 and 37 to discharge the non-condensablegases which collect just above the liquid within them. The liquid isdischarged by these traps through drain main 38 to the coils 10 of theheat exchanger and thence through pipe 39 to a storage tank not Shown orto waste. The non-condensable gases may 'also be discharged throughcoils 10 by connections'such as 40 from air cock 35 to drain main 38. Bythis means the heat in the non-condensable gases and the saturated vaporcommingled with them is conserved, as wellias the heat in the` condensedvapor. It would be impractical to discharge these gases with thecondensed steam without. dlschargin a considerable amount of vapor. Ifit is esired to operate traps are mounted age glasses at the side to fiothe condenser and last effects at less than. l;

pumps to remove both the liquid and condensable gases under a vacuum.

Circulating water flows through shell 5 -over coil 6 of the condenser,the rate of flow being controlled by valve 41 and the circulating waterpump not shown. This circulating water 1s discharged through pipe 42. Inthe case of evaporating apparatus intended primarily for the productionof fresh water, the raw water to be fed through valve 43 may be takenfrom pipe 42. In any case, the rate of feed of the liquid to beevaporated is controlled by valve 43 and a feed pump not shown. Passingthrough the shell 9 of the heat exchanger and the shell 7 of thepreheater, the solution enters the first effect through pipe 44.

The partially evaporated liquid passes from shell 1 through pipe 45 totrap 15 from which itis automatically discharged through pipe 47 toshell 3 of the second effect. Pipe 46 serves to equalize the pressureswithin trap 15 and within shell 1. .A gage glass on the trap 15indicates by the liquid level the proper Working of the bucket or fioatwithin the trap to maintain the proper liquid level within shell l. Fromthe second effect the liquid not evaporated therein is similarlydischarged through pipe 50 to the succeeding effect or to a storage tankor to waste, by trap 16 with supply pipe 48 and equalizing pipe 49. Thevalves 51 and 52 are provided for draining the shells 1 and 3respectively.

Bale 53 within shell 1 prevents columns of liquid being projected intothe vapor space due to the boiling within the 'coils 2 below it. Thevapor -produced is caused by pan 55 to pass to the circumference of theshell, and from the circumference the vapor must pass to the vapor pipethrough a number of perforated openings staggered in two or moreconcentric cylinders 59. The moisture separated thereby drips down intopan 55 and is conveyed by pipe 57 either without the shell or to withinthe solution as shown. Within shell 3, the submerged baiile 54,separator 60, pan 56 and pipe 58 perform similar functions.

Upon shells 1 and 3 are mounted safety valves 61 and 62 so disposed thatthe escaping vapor does not pass through the separators for removingmoisture from the va or before it reaches the vapor pipes. On s ell 1there` is also shown a 4vacuum break'valve 63 to prevent the pressurewithin the shell becoming much less than atmospheric. A similar valvecan be provided on-shell 3.

To the float 64 is attached the valves 65 and 66, the former to throttlethe `-feed and the latter to discharge at first vapor and then liquidshould the latter rise abnormally. The pipe 67 conveys theliquid-discharged to waste or to a storage tank.

Upon the top of the preheater an autoneeds?? matic device 68 is mountedto discharge noncondensable gases collecting therein.

Pressure gages may be provided as at 69l and 70 to aid in the properoperation of the apparatus.`

Referring to Fig. 1, during normal operation of the system, primaryvapor is supplied through main 2O at a pressure slight higher than thatfor which the vapor compressors 11 and 13 are designed to operate. Bythrottling either manually by the valves 21 and 22 or automatically byreducing valves, the pressure is reduced to that for which the De Lavalnozzles in the vapor compressors are designed. This reductlon inpressure near the compressors dries the primary vapor and may somewhatsuperheat it if the drop in pressure is sufficient, thus improving theaction of the compressor. Y

With valves 25, 26, 27, 28 and 29 open, secondary vapor is drawn fromshell 1, compressed, and forced at a higher pressure and temperatureinto coils 2 commingled with the expanded primary vapor from the DeLaval nozzles 12 and 14. Within the coils 2, the commingled vapors arecondensed, the resulting liquid trickling down through the coiled tubesto the trap 17 into which the non-condensable gases are also driven bythe flow of the vapor. It is particularly desirable when vaporcompressors are used, to so arrange the condensing chamber of theevaporator to produce a definite and rather high velocity over thecondensing surface of the vapors to be condensed in order to attain ahigh rate of heat transfer. Also, the noncondensable gases, which areordinarily denser than condensable vapor of the same pressure andtemperature, should be driven downward by the How ofv vapor. Both ofthese objects are obtained by the arrangement of heating surface shownin Fig. 1.

The vertical coiled tube in transmitting heat vto the liquid within thecoils form a column of mingled liquid and vapor less dense than thesolid mass of liquid near the shell. This difference in specific gravityresults in a flow up within the coil and down outside of it, with aconse uent improvement in heat transfer from t e outside surface of thecoil to the solution. This also is particularly advantageous when vaporcompressors are employed.

The columns of mingled liquid and vapor bubbles are prevented from beingprojected into the vapor space by the baffle 53 placed just above thecoils. The va or bubbles are separated to a great extent rom the liquidand escape under the edges of the bale to the vapor space above. Thepank 55 delects the rising vapor to the circumference of the shell, andto reach the vapor pipe the vapor must pass in a number of small streamsthrough the holes or slits in the cylinders 59. The holes or slits arestaggered 1n order to deflect the streams and thus'separate the moisturewhich drips into pan 55 and is conveyed by pipe 57 to within thesolution. The pipe57 may be arran ed to convey the moisture without theshel It is very desirable that the vapor to be compressed by this formof compressor be free from moisture, as is accom lished by the meansdescribed.

Witli valves 24 and 32 closed, a part of the vapor produced in shell 1passes through valves 29 and 31 into the condensing chamber 4 of thesecond effect, where it is condensed by imparting its latent heatthrough the surface ofcoils 4 to the li uid Within shell 3. Of the totaluantity o secondary vapor roduced in she 1 1, from one-half to four-fiths will be compressed by the vapor i compressors and discharged intocoils 2 to be there condensed with the primary vapor, whilel theremainder of the secondary vapor asses to the coils 4 of the secondeffect. gVith the same temperature difference between vapor within thecoils and liquid outside of them in the second effect as in the firsteffect, it is evident that there should be only one-half to one-fifththe condensing surface in the second effect as in the first effect.

The vapor produced in shell 3 by the condensation of secondary vaporfrom shell 1, passes through valve 30 to the coils 6 constituting thecondensingchamber of the condenser having the shell 5. A continuous flowof circulating water is maintained through within the condensinigr shell5 by regulating the valve 41 and the circulating water pump not shown.

Durin normal operation, the liquid resulting rom condensation of thevapor chamber 2 of the first removed by the trap greatest importanceeffect, is automatcal 17; and, what is of t e l 1n an evaporatoroperated by a vapor compressor, the non-condensable gases arecontinuously discharged from directly over the liquid surface where theycollect. This latter is accomplished throu h the cock 35, which isrepresentedv as of t e hand o rated type, but an automatic device mayprovidedl which will allow gas with but very little vapor to escape.Similar traps 18 and 19 with cocks condensed vapor and -non-condensablegases from condensing chambers 4 and 6 respectively.

The condensed va r escapes at a temperature approaching t at of thevapor from which it is formed. Passing throu h drain pipe 38 to thecoils 10 of the eat exchanger, it is cooled `by the incoming feed beforebeing discharged by pipe 39. In some installations it may be desirableto keep separate the condensate from the first eect,

36 and 37 remove the shutting off point. This heating causes aseparation o much of the contained gases, 4.and these are automaticallyremoved by the device-68, or provision for their escape may be made by amanually operated cock at 68. The removal of the gases before theyenterthe evaporator shell improves the performance ofthe vapor compressorswhich would otherwise have to remove them.

Entering the shell 1, the heated liquid boils by reason vof the furtheraddition of heat from the coils 2. The partially evaporated liquidpasses through pipe 45 to the trap 15 from which it is automaticallydischarged through 'Ipipe 47 to the shell 3 of the second effect. heliquid in pipe 45 is denser than the mixture of liquid and vapor bubbleswithin the shell 1. Consequently, the li uid level in 15 will be lowerthan the sur ace of the solution in the shell. The heating surface ismost efficacious when the level Within the shell stands just about thetop of the heating surface, the solution level in the trap 15 andattached gage glass then being from 0 to .10 inchesv lower. In anevaporator employing a vapor compressor, therefore, the most efficientoperation is obtained by maintaining the apparent liquid level asindicated by an external gage glass attached to the shell, from 0 to 10inches Vbelow the -top of the coils.

cording to the concentration desired at pipe 50 The advantages ofproviding two or more vapor compressors are set forth in Patent N o.1,361,843 issued Dec. 14, 1920, filed September 16, 1916, for a singleeffect plant. These advantages also apply to a multiple effect) plant asherein described. Thus assume the'evaporator working at its maximumcapacity with all vapor compressors in operation. The effect of shuttingoff one vapor compressor not only reduces the capacity but alsoincreases the efficiency. This becomes evident when we consider that oneejector reduces the heat to be transferred by the fixed heating surfacein the evaporator. Consequently, the temf increase of efficiency atreduced capacities perature difference between'the solution and.

- sors in parallel for a given capacity the vapor in the heating spaceis reduced with a corresponding reduction in the range of compressionrequired in the vapor compressor. With reduced range of compresincreasestheeliciency ofevaporation with the remaining vapor compressors inoperation. By providing `several vapor compreswith a givenmultiple'effect plant, there is thus vobtained a iexibility of operationwith an not available when a sin le vapor com ressor only is provided.xperiment `s ows that with a single vapor compressor, the capacity oflthe evaporator may be reduced by reducing the initial steam pressurebut the eiiiciencydoes not increase.

above, are intended to take care of certain abnormal conditions. Thus,it may be necessary at times to operate at a greater capacity thanpossible with both compressors workin with rated primary vapor pressure.Wile a slight increase in capacity may be obtained by opening valves 21and 22 wide the 'primary vapo-r suppl a much larger increase may beobtaine by opening valve 23 to by-pass the ejectors with primary vaporto the con'- densing chamber 2 of the first effect. A greatertemperature difference can then be obtainedin the several effects with aconse.

quent increase incapacity but at poorer economy. Instead.v of openingvalve 23,

valve 24 may be opened to admit primary vapor to condensing chamber 4and thus inprime. Connecting the sa ety valve so that crease-thecapacity of the effects succeeding the first, obtaining the desiredincrease in capacity without as great a reduction in economy.

Should for any reason valve 31 be closed during the operation of theplant, the pressure within shell 1 might reach a dangerous point unlesssafety valve 61 opens to discharge the excess vapor. The sudden openingof a safety valve, more especially of theu popping typ'e, causes a veryrapid boiling of the liquid with a conse uent tendency to the largequantity' of vvapor iovv'in'gl to -it does. not` by-pass the separator trough which the vapor leaving the evaporator must pass, reducestheelfect of. primingl This is especially advantageouswhen ejectors areused, as it prevents a large amount'l of the impurealiquid-beingvcarried over into the condensing space to contaminate thecondensed vaportherein. y c

If the trap 15 should 'become-defective and allow the liquid level torisewithin shell 1, the float 64 will also rise when the liquid reachesit, thereby throttling the feed at 65 and at the same time opening anoverfiow valve 66. The escape of vapor from pipe 63 will first serve asa Warning, the liquid later escaping being discharged through pipe 67 toa storage tank orto waste as the case maIy be. v

f the attempt is made to start up the evaporator with valves 25, 26 and29 open, a vacuum will be produced within the shell. The vacuum breakvalve 63 will relieve this vacuum and thusprevent the collapse of ashell not designed sufficiently strong to stand the external pressure.

Pressure gages at 69, 70 and elsewhere serve in properly operating theapparatus.

Having thus described my invention, I claim and-desire to secure byLetters Patent', the following:

1. A plurality of vapor compressors in combination with a multipleeffect evaporat- Various other devices,` not referred to ing plant, eacheffect of said plant 'containing a condensing chamber and an evaporatingchamber, thesaid vapor compressors being connected in parallel towithdraw vapor from the evaporatingl chamber of the first effect andtodischarge the said vapor compressed and commingled with the primaryoperating vapor .into the condensing cham ber of the said first effect,passages being provided for discharging vapor from the evaporatingchamber of each eiect into the condensing chamber of the succeeding eectand from the evaporating chamber of the last effect, and valves beingprovided to reduce the number of vapor compressors in operation.

2. A lurality rof vapor compressors in combination With an evaporatorcontalnlng condensing and evaporating chambers, the .said compressorsbeing connected in parallel to vWithdraw vapor from the said evaporatingchamber and to discharge the said vapor number of vapor compressors inoperation,

and means of preheatin the liquid fed to the said evaporating cham r bythe condensation of' vapor from the said condensing chamber.

3. In an evaporating apparatus comprising a vapor compressor containinga De Laval nozzle incombination with an evaporator containing condensingand evaporating chambers, means of giving Warning of an abnormal rise ofliquid in the said evapo rating chamber by automatically dischargingvapor therefrom.

WiLLiAM L. DE BAUFRE.

v'Witnesses H. ASTURT, I WIN'rmorCoBn.

